Hydrophobized fiber cement product comprising at lease one profiled surface

ABSTRACT

A method for improving the hydrophobic properties of a fiber cement product, is provided. The method comprises the steps of providing a fiber cement product comprising at least one profiled surface, applying a water-free silane-based liquid to the at least one profiled surface, and allowing said water-free silane-based liquid to penetrate into the fiber cement product.

FIELD OF THE INVENTION

The present invention relates to fiber cement products, having improvedhydrophobic properties and to methods to improve the hydrophobicproperties of such fiber cement products.

BACKGROUND OF THE INVENTION

Fiber cement products are well known. However under some weatherconditions, typically under humid conditions, water can penetrate intothe fiber cement matrix of the product. In general, fiber cementproducts need to be protected to penetrating water, as the water maynegatively influence the mechanical properties, resistance to weatherconditions such as frost, the aging of the product and in some cases theappearance of the fiber cement product.

As an example, by slowly dissolving salts present in the matrix, thewater can function as a carrier to bring the salts to the surface. Thiseffect, called efflorescence, causes white traces to become visible onthe surface.

To avoid these negative effects, agents which cause the fiber cementproduct to be more hydrophobic, hydrophobation agents, are used andapplied to the surface of the fiber cement product. As such, water is toa large extent prevented to penetrate into the fiber cement matrix,reducing the efflorescence to a large extent.

However it was noticed that, when applying typical hydrophobation agentsto a profiled, such as milled, surface, the hydrophobation agent itselfleaves traces in the surface after being applied and dried.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a fiber cementproduct having at least one profiled, typically milled, surface, towhich a hydrophobation agent is applied without leaving traces of thishydrophobation agent.

According to the first aspect of the present invention, a method forimproving the hydrophobic properties of a fiber cement product isprovided. The method comprises the steps of

-   -   Providing a fiber cement product comprising at least one        profiled surface;    -   Applying a water-free silane-based liquid to the at least one        profiled surface;    -   Allowing said a water-free silane-based liquid to penetrate into        the fiber cement product.

The water-free silane-based liquid is allowed to penetrate in to thepores of the fiber cement matrix along the outer profiled surface of thefiber cement product.

The term liquid refers to a liquid state under ambient temperature (21°C.) and at ambient pressure (1035 hPa). Matter is a liquid under theseconditions when its volume remains constant while its shape adopts tothe container in which it is provided.

According to some embodiments of the present invention, the water-freesilane-based liquid may be a solvent-free silane-based liquid.

When a silane- and/or siloxane-base, water diluted liquid is used, itwas found that white residue traces were noticed on the profiled surfaceof the fiber cement product. Using solvent diluted silane- and/orsiloxane-based liquids to provide improved hydrophobic properties to thefiber cement product, often, but not always, discolored spots arevisible. Both visual effects are noticed as defects, causing the fibercement product to be either rejected or considered as impaired. Thewater-free and preferably solvent-free silane-based liquid comprises oneor more silanes (SiR₄, each of the 4 R-groups independently being anorganic group), and may further comprise on or more oligomer siloxanes(H(R₂SiO)_(n)OH, each of the R-groups independently being an organicgroups). According to preferred embodiments, the water-free andpreferably solvent-free silane-based liquid may comprise or even mayconsist of alkyltriethoxysilane.

More preferred, the used water-free, and preferably also solvent-freesilane-based liquid comprises at least 50% w, even more than 75% w ofsilanes. Most preferred, the water- and solvent-free silane-based liquidcomprises 99% w or more of silanes.

The water-free and preferably also solvent-free silane-based liquidprovides the treated surface with improved hydrophobic properties. Thewater-free and preferably also solvent-free silane-based liquid is usedas a so-called hydrophobation agent.

It was found that other hydrophobation agents were not suitable for useon profiled fiber cement products, in particularly not on surfaces whererecesses and/or groves are milled. The other hydrophobation agents werenot able to penetrate in the fiber cement material along the insidecorners of the recessions, leaving traces of polymerized hydrophobationagent.

Though the reason is not fully understood, water-free and preferablyalso solvent-free silane-based liquid, when used as hydrophobation agenton profiled fiber cement products, in particularly having recesses orgroves along its surface, was found to penetrate in the fiber cementmaterial also along the inside corners of the recessions, withoutleaving visual traces.

The fiber cement products obtainable by the method according to thefirst aspect of the present invention may have an average density in therange of 0.35 kg/m³ to 2 kg/m³, such as between 0.4 kg/m³ and 1.9 kg/m³.The average density is the density at average over a representativesurface and thickness. The product at its profiled surface may have adensity slightly higher as the density throughout the product at the nonprofiled volumes and surfaces. This due e.g. the profiling action, suchas milling and alike.

The benefit of the use of water-free and preferably also solvent-freesilane-based liquid is best noticeable for fiber cement products havinghigher density. The fiber cement products obtainable or obtained using amethod according to the invention preferably have a density in the rangeof 0.9 kg/m³ to 2 kg/m³, such as in the range of 1.1 kg/m³ to 1.95kg/m³, more preferred in the range of 1.15 kg/m³ to 1.9 m/kg³.

The fiber cement products have a hydrophobic property expressed as thefiber cement product having a water take up of less than 1.5 ml after 48h using the RILEM Test No 11.4 in horizontal application. Preferably thewater take up is even less than 1 ml per 48 h according to this test.

This is obtained using water-free and preferably also solvent-freesilane-based liquid as hydrophobation agent. When the water-free andpreferably also solvent-free silane-based liquid also comprisedsiloxanes, a significant improvement of the beading effect can beobtained.

According to some embodiments of the present invention, the water-freesilane-based liquid may be applied to the at least one profiled surfacein an amount of less than 150 g/m², and more than 10 g/m².

More preferred less than 120 g/m² or even less than 90 g/m² is appliedto the profiled surface. More preferred more than 40 g/m² or even morethan 50 g/m² or even more than 60 g/m² is applied to the profiledsurface.

It is understood that also the other sides and surfaces of the fibercement product, in particular when the product is a fiber cement plate,can be treated with the same or a different hydrophobation agent.

The fiber cement product can be any type of product, but typically is aproduct having a planar shape.

According to some embodiments of the present invention, the fiber cementproduct may be a fiber cement plate.

Fiber cement plates are well known in the art. The fiber cement productsare made out of fiber cement slurry, which is formed in a so-calledgreen fiber cement product, and cured.

Dependent to some extent on the curing process used, the fiber cementslurry typically comprises water, process or reinforcing fibers whichboth may be natural organic fibers (typically cellulose fibers) orsynthetic organic fibers (polyvynilalcohol, polyacrilonitrile,polypropylene, polyamide, polyester, polycarbonate, polyethylene, etc.),cement e.g. Portland cement, limestone, chalk, quick lime, slaked orhydrated lime, ground sand, silica sand flour, quartz flour, amorphoussilica, condensed silica fume, microsilica, metalkaolin, wollastonite,mica, perlite, vermiculite, aluminum hydroxide, pigments, anti-foamingagents, flocculants, and other additives.

The green fiber cement product is cured, typically by curing to the air(air cured fiber cement products) or under pressure in presence of steamand increased temperature (autoclave cured). For autoclave curedproducts, typically sand is added in the fiber cement slurry. Theautoclave curing typically results in the presence of 11.3 Å (angstrom)Tobermorite in the fiber cement product.

Fiber cement plates usually are made using the well knownHatschek-process, flow-on process or Magnani-process.

According to embodiments, the fiber cement plate may have at least oneflat, non profiled surface. This least one flat, non profiled surfacemay be present opposite to the profiled surface of the fiber cementproduct.

The fiber cement plate may preferably have a thickness up to 45 mm. Thefiber cement plate according to the invention may have a thickness up toand including 35 mm, optionally only up to and including 30 mm, or evenonly up to and including 25 mm, a height typically up to 4 m and a widthtypically up to 1.5 m. Most preferred the thickness of the plate are inthe range of 4 mm to 40 mm, such as in the range of 5 mm to 35 mm, e.g.in the range of 5 mm to 20 mm, more preferred in the range of 5 mm to 16mm, e.g. 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mmor 15 mm. The height of the fiber cement plate may preferably be in therange of 1.5 m to 4 m, most preferred in the range of 2 m to 4 m, e.g.in the range of 2.5 m to 3.7 m, e.g. 2.5 m, 2.6 m, 2.7 m, 2.8 m, 2.9 m,3.0 m, 3.1 m, 3.2 m, 3.3 m, 3.4 m, 3.5 m, 3.6 m and 3.7 m. The width ofthe fiber cement plate may preferably be in the range of 0.6 m to 1.75m, most preferred in the range of 0.6 m to 1.5 m, e.g. in the range of0.75 m to 1.5 m, e.g. 1.0 m, 1.1 m, 1.2 m, 1.3 m, 1.4 m or 1.5 m.

Preferably the fiber cement product is a fiber cement plate, having twosubstantially flat surfaces, of which one or two, preferably only one,is provided with a profile. The profile may be a random or random-likeprofile. An example of such profile may be the profile of timber.

Alternatively the profile is a repetitive profile, such as acheckerboard profile with locally sunk rectangular or square surfaces.

The profile may comprise sunk parts or surfaces, delimited by flankshaving an angle between the sunk surface and the flank in the range of90° to about 180°, preferably more than 90°, such as more than 95° ormore than 100°, and less than 175° such less than 170° or less than 165°such as less than 160° even less than 155° or less than 150°. The inner,as well as potentially outer corners may have a sharp delimitation, ormay be rounded, typically with a small bending radius.

According to some embodiments of the present invention, the fiber cementproduct may be a fiber cement plate having at least one surfacecomprising at least one groove. According to some embodiments of thepresent invention, the profiled surface comprises a plurality of groovesbeing equally distributed over the surface, the grooves all have auniform direction and a uniform depth.

The grooves may have a cross section in a section according to a planeperpendicular to the direction of the groove being triangular,trapezoid, rectangular or square, elliptic, circular, or alike.

According to some embodiments of the present invention, the grooves mayhave a trapezoid cross section in a section according to a planeperpendicular to the direction of the groove, the groove having a flatbottom and two flanks, the angles between the bottom and each of theflanks is in the range of 90° to about 180°, preferably more than 90°,such as more than 95° or more than 100°, and less than 175° such lessthan 170° or less than 165° such as less than 160° even less than 155°or less than 150°.

The depth of the grooves is preferably more than 0.1 mm, and morepreferred in the range of 0.15 mm to 1.0 mm, such as between 0.15 mm andto 0.5 mm. The maximum width at the bottom of the groove is preferablyin the range of 2 mm to 20 mm, and most preferred in the range of 4 mmto 15 mm.

As an example, the grooves may have a trapezoid cross section anddistributed at equal distances one to the other. As such the profile ofa section according to a plane perpendicular to the direction of thegroove will have a step-wave shape.

The width of the top surfaces between adjacent grooves is preferablymore than 1 mm, typically more than 2 mm or more than 3 mm.

According to some embodiments of the present invention, the water-freesilane-based liquid may penetrate at least 1 mm into the profiledsurface.

According to some embodiments of the present invention, the fiber cementproduct may be an autoclave cured fiber cement product. Alternativelythe fiber cement product may be an air cured fiber cement product.

According to some embodiments of the present invention, the fiber cementproduct may be obtained using a Hatschek process. According to someembodiments of the present invention, the fiber cement product may beobtained using a flow-on process. According to some embodiments of thepresent invention, the fiber cement product may be obtained using aMagnani-process.

According to some embodiments of the present invention, applying thewater-free silane-based liquid may be done by spraying the water-freesilane-based liquid to the profiled surface.

Such spraying may be done by means of any known spraying installation.Given the profiled surface to be sprayed, the spraying nozzles may haveangled positions in view of the surface to be sprayed to guarantee anequal amount of liquid to be sprayed over the profiled surface.Optionally the spraying nozzles may have a dynamically changeableorientation.

According to some embodiments of the present invention, applying thewater-free silane-based liquid may be done by brushing or rolling thewater-free silane-based liquid to the profiled surface.

The brushes and/or rollers preferably needs to be sufficiently soft,flexible and/or compressible to allow them to contact the profiledsurface also in the lower sunken parts.

According to some embodiments of the present invention, the provision ofa fiber cement product comprising at least one profiled surface maycomprise the provision of a green fiber cement plate using a Hatscheckprocess, and profiling at least one surface of the fiber cement plateafter curing of the green fiber cement plate.

A green fiber cement product is to be understood as the product obtaineddirectly after shaping the product, but before the cement is cured.

The green fiber cement product may be pressed before curing.

According to some embodiments of the present invention, the green fibercement plate may be cured using autoclave curing.

According to some embodiments of the present invention, the profiledsurface may be provided by milling the fiber cement product.

The fiber cement product according to the invention has at least one,and possibly more than one surface which is profiled, typically milledor grinded.

The fiber cement product comprising at least one profiled surface whichis preferably provided after curing the cement of the fiber cementproduct. Such profiled surface is to be understood as a post-curingprofiled surface.

The profiled surface may be provided by profiling a surface of the greenfiber cement product, by pressing a profile in to the surface of thegreen fiber cement product. It may even be profiled during production ofthe green fiber cement product, e.g. by using equipment with profiledsurfaces which contacts the fiber cement slurry during the provision ofthe green fiber cement product.

Most preferably the profiled surface is provided after curing of thegreen fiber cement product. This is typically done by milling.

The milling can be done using suitable milling tools such as millingcutters, typically having hard metal of diamond coated cutting surfaces.

According to a second aspect of the present invention, a fiber cementproduct obtained according to the first aspect of the present inventionis provided.

According to a second aspect of the present invention, a fiber cementproduct is provided, which comprising at least one profiled surface, thefiber cement product comprises a porous fiber cement matrix along the atleast one profiled surface characterized in that water-free silane-basedhydrophobic agent, originating from a water-free silane-based liquid, ispresent in the pores of the matrix along the at least one profiledsurface.

According to some embodiments of the present invention, the profiledsurface may be free of silane- and siloxane-residue.

The independent and dependent claims set out particular and preferredfeatures of the invention. Features from the dependent claims may becombined with features of the independent or other dependent claims,and/or with features set out in the description above and/or hereinafteras appropriate.

The above and other characteristics, features and advantages of thepresent invention will become apparent from the following detaileddescription, taken in conjunction with the accompanying drawings, whichillustrate, by way of example, the principles of the invention. Thisdescription is given for the sake of example only, without limiting thescope of the invention. The reference figures quoted below refer to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is schematically a top-view of a profiled fiber cement product,having one post-curing profiled surface, according to the invention.

FIG. 1b is schematically a side-view of a part of this profiled fibercement product of FIG. 1a , having one post-curing profiled surface,according to the invention.

FIG. 2 is a schematically view of a process to improve the hydrophobicproperties of a profiled fiber cement product, having one post-curingprofiled surface, according to the invention

The same reference signs refer to the same, similar or analogouselements in the different figures.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention will be described with respect to particularembodiments.

It is to be noticed that the term “comprising”, used in the claims,should not be interpreted as being restricted to the means listedthereafter; it does not exclude other elements or steps. It is thus tobe interpreted as specifying the presence of the stated features, stepsor components as referred to, but does not preclude the presence oraddition of one or more other features, steps or components, or groupsthereof. Thus, the scope of the expression “a device comprising means Aand B” should not be limited to devices consisting only of components Aand B. It means that with respect to the present invention, the onlyrelevant components of the device are A and B.

Throughout this specification, reference to “one embodiment” or “anembodiment” are made. Such references indicate that a particularfeature, described in relation to the embodiment is included in at leastone embodiment of the present invention. Thus, appearances of thephrases “in one embodiment” or “in an embodiment” in various placesthroughout this specification are not necessarily all referring to thesame embodiment, though they could. Furthermore, the particular featuresor characteristics may be combined in any suitable manner in one or moreembodiments, as would be apparent to one of ordinary skill in the art.

When reference is made to a range, unless otherwise specified, the rangeis to be understood inclusive.

The fiber cement product, being a fiber cement plate 100 in FIG. 1,comprises one profiled surface 102, provided by milling of the trapezoidlike grooves 110 after the fiber cement plate 100 was cured in anautoclave. The cured fiber cement product before milling is obtainablefrom Eternit NV as EQUITONE [Tectiva].

After having been milled using appropriate milling tools, the profiledsurface 102 is provided with an hydrophobation agent being water-freesilane-based liquids. The used liquids are set out in table 1.Hydrophobation agents used in test 4 to 9 are water-free silane-basedliquids, i.e. according to a method of the present invention.Hydrophobation agents in test 4, 6, 7 and 8 are also solvent-free.

In each case, this product is applied by spraying the liquid to theprofiled surface. The profiled surface has a width E of 1.22 m and aheight L of 2.5 m, resulting in a surface of 3.05 m². The amount ofliquid, per such surface unit of the profiled surface was 80 g/m².

TABLE 1 Hydrophobation agent # W % active test Water/ Active ingredientin # Product name solvent born ingredient(s) liquid applied 1 DC520 ¹Water born Silane & 16 siloxane 2 DC520 + Water born Silane & 16 IE6682¹ siloxane 3 IE6682 ¹ Water born silane 16 4 Z6341 ¹ Waterfree & silane100 solventfree 5 Funcosil Solvent born Silane & 7 SNL ² siloxane 6Protectosil Waterfree & silane 100 BHN ³ solventfree 7 ProtectosilWaterfree & silane 100 BHN ³ solventfree 8 Protectosil Waterfree &silane 100 100NK ³ solventfree 9 Z6689/MR2404 ¹ Solvent born silane 7.5¹ available from Dow Corning; ² available from Remmers ³ available fromDemula/Evonik

After having allowed the liquid to penetrate into the profiled surface,the liquid has penetrated into the surface up to an average depth D, assuch providing a zone 120 in which the hydrophobation agent is presentin the porous fiber cement matrix.

The profiled surfaces are tested on hydrophobicity using the RILEM TestNo 11.4 in horizontal application. Also the presence of white residue ofthe hydrophobation agent was noted (yes or no), and the beading effectof the hydrophobation agent was characterized using a ranking of 1(water droplets are either soaked up by the surface or remain present asdroplets with contact angle of 90° or less between surface and droplet)to 5 (droplets remain on surface as beads, the contact angle beingsubstantially 180°). The results are set out in table 2.

The contact angle between a surface Sx and the outer surface of adroplet is the angle between the tangent, at the contact point betweensurface Sx and the droplet surface, of the curve obtained by making asection of the outer surface of the droplet and a plane perpendicular tothe surface Sx, the angle being the angle oriented towards the dropletvolume.

TABLE 2 results Rilem test White residue Beading; visual test after 48 hpresent? assessment # (ml) (y/n) (1 to 5) 1 0.3 Y 4 2 0.4 Y 3 3 0.45 Y 24 0.23 N 4 5 0.35 N 4 6 0.28 N 3 7 0.28 N 2 8 0.3 N 5 9 0.4 N 5

As is noticeable, the tests 4 to 9, using a water-free, silane basedhydrophobation agent, no white residue of the hydrophobation agent isleft.

As can be seen in FIGS. 1a and 1b , the profile is a step-wave profile122 having trapezoid like grooves 110 with a recess depth R of 2 mm, atop width T of 8 mm and a recess width W of 12 mm. The total thickness Aof the plate 100 is 10 mm, and a remaining thickness B at the lowersurface or bottom 124 of the groove of 8 mm. The inclination angle αbetween the bottom 124 and each of the flanks 126 and 128 is 110°, thusproviding slopes with a slope width S.

A schematic view of the method to provide the fiber cement productsaccording to the invention is shown in FIG. 2.

The method for improving the hydrophobic properties of a fiber cementproduct, comprises first the step 200 of providing a green fiber cementproduct, preferably a plate. This may be done by a Hatscheck process.

This green plate may optionally be compresses in the optional step 210,after which the green fiber cement plate is cured by means of air curingor autoclave curing in step 220.

In a next step 230, the cured product is given a profiled surface bye.g. milling. Thereafter in a next step 240 water-free, silane basedhydrophobation agents are applied, e.g. by spraying to the at least oneprofiled surface.

The applies hydrophobation agent is allowed to penetrate in step 250 anda product according to the present invention is obtained. Thehydrophobation agent is penetrated through the surface into the pores ofthe fiber cement matrix of the fiber cement product. At the surface, novisual residue of the hydrophobation agent is left.

It is to be understood that although preferred embodiments and/ormaterials have been discussed for providing embodiments according to thepresent invention, various modifications or changes may be made withoutdeparting from the scope and spirit of this invention.

1: A method for improving the hydrophobic properties of a fiber cementproduct, said method comprising the steps of: providing a fiber cementproduct comprising at least one profiled surface; applying a water-freesilane-based liquid to the at least one profiled surface; and allowingsaid water-free silane-based liquid to penetrate into the fiber cementproduct. 2: A method according to claim 1, wherein said water-freesilane-based liquid is a solvent-free silane-based liquid. 3: A methodaccording to claim 1, wherein the water-free silane-based liquid appliedto the at least one profiled surface is in an amount of less than 150g/m², and more than 10 g/m. 4: A method according to claim 1, whereinthe fiber cement product is a fiber cement plate. 5: A method accordingto claim 4, wherein the fiber cement plate has at least one surfacecomprising at least one groove. 6: A method according to claim 1,wherein the profiled surface comprises a plurality of grooves beingequally distributed over said surface, said grooves all having a uniformdirection and a uniform depth. 7: A method according to claim 6, whereinsaid grooves have a trapezoid cross section according to a planeperpendicular to the direction of the groove, said groove having a flatbottom and two flanks, the angles between the bottom and each of saidflanks is in the range of 90° to about 180°. 8: A fiber cement productaccording to claim 1, wherein the fiber cement product is an autoclavecured fiber cement product. 9: A method according to claim 1, whereinapplying said water-free silane-based liquid is done by spraying saidwater-free silane-based liquid to the profiled surface. 10: A methodaccording to claim 1, wherein applying said water-free silane-basedliquid is done by brushing or rolling said water-free silane-basedliquid to the profiled surface. 11: A method according to claim 1,wherein the provision of a fiber cement product comprising at least oneprofiled surface comprises the provision of a green fiber cement plateusing a Hatscheck process, and profiling at least one surface of saidfiber cement plate after curing of the green fiber cement plate. 12: Amethod according to claim 11, wherein the green fiber cement plate iscured using autoclave curing. 13: A method according to claim 1, whereinthe profiled surface is provided by milling the fiber cement product.14: A fiber cement product obtained according to claim
 1. 15: A fibercement product comprising at least one profiled surface, said fibercement product comprising a porous fiber cement matrix along said atleast one profiled surface, characterized in that a water-freesilane-based hydrophobic agent is present in the pores of said matrixalong said at least one profiled surface. 16: A fiber cement productaccording to claim 15, wherein the profiled surface is free of silane-and siloxane-residue. 17: The use of water-free silane-based liquid toimprove the hydrophobic properties of the profiled surfaces of a fibercement product having at least one profiled surface.